/*

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.

s = "loveleetcode",
return 2.
Note: You may assume the string contain only lowercase letters.

 */

class Solution {
    public int firstUniqChar(String s) {

        int[] freq = new int[26];

        for (int i = 0; i < s.length(); i ++)
            freq[s.charAt(i) - 'a'] ++;

        for (int i = 0; i < s.length() ; i ++)
            if (freq[s.charAt(i) - 'a'] == 1)
                return i;


        return -1;

    }
} 